Questions and discussion for this lecture live here. Fire away by hitting Reply below
I thought the external work would be P•d /2 and not P•d?
You have also assumed that member AB is significantly longer than member BC. What if you had an equilateral triangle where the changes in length for members AB and BC become comparable … ? How does that affect the assumptions made?
No - the work done by a force is the product of the force magnitude and the distance travelled along the line of action of the force, P*d.
The virtual work method applied to truss analysis doesn’t rely on any assumptions about relative member length - you can apply it to an equilateral triangle without any issues.
S